Toy building block



FIG. 1 is a perspective view of a toy building block embodying the new design;

FIG. 2 is a front side view thereof, the back side view being a mirror image thereof;

FIG. 3 is a left side view thereof, the right side view being a mirror image thereof; and,

FIG. 4 is a top plan view thereof, the bottom plan view being a mirror image thereof.

The broken lines in FIGS. 1-4 are included for the purpose of illustrating portions of the toy building block which form no part of the claimed design. 

CLAIM The ornamental design for a toy building block, as shown and described. 